Effective Catalytic Degradation Of Organic Dyes And Coupled Production Of Hydrogen By Nano Zero Valent Iron-Encapsulated Composite Membrane

Nano zero valent iron（nZVI）possesses potential toxicity and is a threat to aquatic organisms,it is also easy to be oxidized,tends to agglomerate and difficult to recover.A dispersion and loading method of nano zero valent iron with acceptable cost is necessary and promising,which would reduce the loss of particles and improve the recycling performance.Electrospinning integrated molding technology can produce fiber skeleton with excellent performance and effectively improve the application ability of nZVI in aqueous environment.In this paper,fiber skeleton dispersed nano zero valent iron materials were prepared and characterized by in-situ method.The composite membrane was applied to oxidative decolorization of organic dyes and synergistic hydrogen production were studied.The main research contents and findings are as below:（1）Polyacrylonitrile/nano zero valent iron nanocomposites（PAN@Fe⁰）were successfully prepared by in-situ synthesis method.When compared with commercial nano zero valent iron（with surface-coated organic layer）,nZVI in PAN@Fe⁰ has better dispersion and smaller particle size.After loading nZVI particles,the diameter of polyacrylonitrile nanofiber increased and the magnetism properties were improved.However,in general,the nanofiber structure could minimize the agglomeration,dropping and lossing,facilitate material recovery and reduce the risk of secondary pollution.The introduction of particles didn’t significantly change the surface morphology,fiber structure and chemical composition of the fiber.The intrinsic properties of Fe⁰ can be weakened due to the encapsulation structure.Acid etching could preferably expose the internal active sites and promote the applications.（2）PAN@Fe⁰ nanofibrous composites could play an important role in oxidation process of Rhodamine B（Rh B）,with strong catalytic ability for three kinds of Fenton-like systems（H₂O₂,Na₂S₂O₈ and NaCl O₂）.The degradation rate constants K of Rh B were 0.0140min^-1,0.0547 min^-1 and 0.3155 min^-1,respectively.1.5m M NaCl O₂ could degrade 50mg·L^-1 Rh B in 15min,better than the other two degradation systems.The main active species in the three systems are·OH,SO₄·^-and Cl O₂·.The chemical adsorption of Rh B was the main rate limiting step,and photocatalytic oxidation was the main degradation process.In five cycles,the maximum nZVI shedding amount below 0.55%,indicating the good stabilization of nZVI.（3）PAN@Fe⁰ nano mat could also play an important role in the process of simultaneous degradation of organic pollutants and synergistic hydrogen production in the NaBH₄-organic（4-nitrophenol（4-NP）,Rhodamine B,methylene blue（MB））systems,and there existed a coupling equilibrium point between the two processes.The synchronization of pollution reduction and hydrogen production capacity significantly enhance the atomic economy.The hydrogen production process of NaBH₄ catalytic hydrolysis was affected by mass transfer and heat transfer.The activation energy was 33.713 KJ·mol^-1.A linear relationship was performed between the hydrogen generation rate and the temperature/sodium borohydride concentration/catalyst dosage.The hydrogen atom utilization efficiency was 60.80%when hydrogen production equilibrium reached.The reduction process of organic matter followed pseudo-first-order kinetics and the degradation capacity to different pollutants was:Rh B>4-NP>MB.The degradation process was a heterogeneous catalytic process and followed the surface reaction-controlled Langmuir-Hinshelwood（L-H）model,H₂ and H·played the synergistic role.